Typhoon Haiyan caused widespread devastation because no one had anticipated the height of the waves or the strength of the storm surge, the UN's head of disaster risk in south-east Asia has admitted.

Jerry Velasquez said: "In the past, early warning systems were based on wind speeds, and then in 2011 this was changed [to take into account waves]. New equipment was put in but there was very little experience on storm surges."

He said the country's 2013 disaster budget, of about $171m (£107m), had been used up on previous weather-related disasters. "The last category 5 typhoon was in 2005, killing 750 people. This one did $12-15bn of damage and will cost 5% of GDP. Only $2bn was insured and 80% of that loss will be born by the poor people."

Velasquez was in London as a German government-funded thinktank Germanwatch released its 2014 vulnerability index. It ranked the Philippines second for weather related loss last year, largely as a result of typhoon Bopha, which killed more than 1,400 people last December. Haiti was the worst affected country in 2012, after taking the full force of hurricane Sandy, even though the damage done when it crossed to the US was far greater in financial terms.

The report says: "Haiti, the poorest country in the western hemisphere, was still coping with the aftermath of the earthquake of 2012, it suffered losses of about $7.5m, the equivalent of about 10% of its GDP. The landfall of hurricane Sandy in the US dominated international news in October 2012. Yet, it was Haiti – the poorest country in the western hemisphere – that suffered the greatest losses from the same event."

But the report, launched this week in Warsaw at the UN climate talks, showed the Philippines rising dramatically up the global risk index list, supporting the government's claims that typhoons are becoming stronger. Between 1992 and 2011, the Philippines ranked 14th, but over the past 13 years it has been the seventh worst-hit country behind Honduras, Myanmar, Haiti, Nicaragua, Bangladesh and Vietnam.

According to Velasquez, fewer people are dying worldwide because of climate-related disasters, but far more are exposed than a decade ago, and the economic impact is soaring. "Losses amounted to more than $1.75tn in original values," he said.

Germanwatch calculates that more than 530,000 people have died as a direct result of some 15,000 extreme weather events between 1993 and 2012. The thinktank said: "Eight of the 10 countries most affected by extreme weather between 1993-2012 were developing countries in the low-income or lower middle-income group, while only two were upper middle-income countries."

It added: "In relative terms, poorer developing countries are hit much harder despite the fact that the absolute monetary damages are much higher in richer countries. Loss of life and personal hardship is also much more widespread especially in low-income countries."

The study suggests two groups of vulnerable countries are emerging: those that are continuously affected by extreme events such as Bangladesh, Honduras and Haiti; and others, such Myanmmar and Thailand, which rank high because of exceptional catastrophes.

The report also notes that Fiji and Samoa are often affected by extreme weather because of their exposure to the south Pacific tropical cyclone season. Both islands were hit hard by cyclone Evan, the worst in 20 years, causing damages of 20% of Samoa's GDP. Nigeria was included in the top 10 for 2012 owing to heavy rains, which triggered its worst floods in 50 years and displacing over 2 million people.

"One of the underlying causes of disasters is the pattern of development, which encourages short-term thinking and actually aggravates risk," said Velasquez. "The pace of the creation of exposure to risk has become far greater than the reduction of vulnerability. We are not reducing vulnerability."

The report connects natural disasters to climate change but says it is not possible to attribute disaster to climate change. However, it says there was high confidence that the Middle East's driest winter in more than 1,900 years in 2008, the record-breaking summer heat and drought in the US in 2011, and Europe's hottest summer in more than 500 years in 2003 were all attributable to climate change.

The release of the report coincided with the World Meteorological Organisation's provisional assessment of 2013. "Temperatures so far this year are about the same as the average during 2001 to 2010, which was the warmest decade on record," said the secretary-general, Michel Jarraud. "All of the warmest years have been since 1998 and this year once again continues the underlying, long-term trend. The coldest years now are warmer than the hottest years before 1998."

Jarraud added: "Atmospheric concentrations of carbon dioxide and other greenhouse gases reached new highs in 2012, and we expect them to reach unprecedented levels yet again in 2013. This means that we are committed to a warmer future.

"Surface temperatures are only part of the wider picture of our changing climate. The impact on our water cycle is already becoming apparent – as manifested by droughts, floods and extreme precipitation."